Akka/Scala example source code file (UdpListener.scala)

This example Akka source code file (UdpListener.scala) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Akka and Scala source code examples by using tags.

All credit for the original source code belongs to akka.io; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Akka tags/keywords

actor, actorref, akka, channelregistration, channelregistry, datagramchannel, dispatch, inetsocketaddress, io, nonfatal, receive, successfully, unbound, unit, util, utilities

The UdpListener.scala Akka example source code

/**
 * Copyright (C) 2009-2014 Typesafe Inc. <http://www.typesafe.com>
 */
package akka.io

import java.net.InetSocketAddress
import java.nio.ByteBuffer
import java.nio.channels.DatagramChannel
import java.nio.channels.SelectionKey._
import scala.annotation.tailrec
import scala.util.control.NonFatal
import akka.actor.{ ActorLogging, Actor, ActorRef }
import akka.dispatch.{ RequiresMessageQueue, UnboundedMessageQueueSemantics }
import akka.util.ByteString
import akka.io.SelectionHandler._
import akka.io.Udp._

/**
 * INTERNAL API
 */
private[io] class UdpListener(val udp: UdpExt,
                              channelRegistry: ChannelRegistry,
                              bindCommander: ActorRef,
                              bind: Bind)
  extends Actor with ActorLogging with WithUdpSend with RequiresMessageQueue[UnboundedMessageQueueSemantics] {

  import udp.bufferPool
  import udp.settings._

  def selector: ActorRef = context.parent

  context.watch(bind.handler) // sign death pact

  val channel = DatagramChannel.open
  channel.configureBlocking(false)

  val localAddress =
    try {
      val socket = channel.socket
      bind.options.foreach(_.beforeDatagramBind(socket))
      socket.bind(bind.localAddress)
      val ret = socket.getLocalSocketAddress match {
        case isa: InetSocketAddress ⇒ isa
        case x                      ⇒ throw new IllegalArgumentException(s"bound to unknown SocketAddress [$x]")
      }
      channelRegistry.register(channel, OP_READ)
      log.debug("Successfully bound to [{}]", ret)
      ret
    } catch {
      case NonFatal(e) ⇒
        bindCommander ! CommandFailed(bind)
        log.debug("Failed to bind UDP channel to endpoint [{}]: {}", bind.localAddress, e)
        context.stop(self)
    }

  def receive: Receive = {
    case registration: ChannelRegistration ⇒
      bindCommander ! Bound(channel.socket.getLocalSocketAddress.asInstanceOf[InetSocketAddress])
      context.become(readHandlers(registration) orElse sendHandlers(registration), discardOld = true)
  }

  def readHandlers(registration: ChannelRegistration): Receive = {
    case SuspendReading  ⇒ registration.disableInterest(OP_READ)
    case ResumeReading   ⇒ registration.enableInterest(OP_READ)
    case ChannelReadable ⇒ doReceive(registration, bind.handler)

    case Unbind ⇒
      log.debug("Unbinding endpoint [{}]", bind.localAddress)
      try {
        channel.close()
        sender() ! Unbound
        log.debug("Unbound endpoint [{}], stopping listener", bind.localAddress)
      } finally context.stop(self)
  }

  def doReceive(registration: ChannelRegistration, handler: ActorRef): Unit = {
    @tailrec def innerReceive(readsLeft: Int, buffer: ByteBuffer) {
      buffer.clear()
      buffer.limit(DirectBufferSize)

      channel.receive(buffer) match {
        case sender: InetSocketAddress ⇒
          buffer.flip()
          handler ! Received(ByteString(buffer), sender)
          if (readsLeft > 0) innerReceive(readsLeft - 1, buffer)
        case null ⇒ // null means no data was available
      }
    }

    val buffer = bufferPool.acquire()
    try innerReceive(BatchReceiveLimit, buffer) finally {
      bufferPool.release(buffer)
      registration.enableInterest(OP_READ)
    }
  }

  override def postStop(): Unit = {
    if (channel.isOpen) {
      log.debug("Closing DatagramChannel after being stopped")
      try channel.close()
      catch {
        case NonFatal(e) ⇒ log.debug("Error closing DatagramChannel: {}", e)
      }
    }
  }
}